Telephone system



Aug. 18, 1931. 'r. A. LUNDELL 1,819,685

TELEPHONE SYSTEM Filed Jan. 3 193 6 Sheetg-Sheet 1 lNveN-rark Aug. 18,1931. 1-. A. LUNDELL TELEPHONE SYSTEM Filed Jan. 3 1930 6 Sheets-Sheet 2a 3 w w u H 3 4 1 0 J Jr E 4 v z II a. M 7 I "mm 1 z LKl M L ML 5 H a 71 ,7 a -Tiiiiiiii. a M m. a M r n J M I. w 3+ "w "w 0 W H 49 0 4 w H L am 7 fl no ell lNveNrdK Aug. 18, 1931. A. LUNDELL 1,819,635

TELEPHONE SYSTEM Filed Jan. 3 1950 6 Sheets-Sheet 3 '7 jam Jel/nvverlrug Aug. 18, 1931. T. A. LUNDELL 1,819,635

TELEPHONE SYSTEM Filed Jan. 3 930 6 Sheets-Sheet 4 1': f :TTIL

Aug. 18, 1931. 1'. A. LUNDELL TELEPHONE SYSTEM Fild Jan. 3, 1930 6Sheets-She'et 5 Aug. 18, 1931. 'r. A. LUNDELL 1,819,685

TELEPHONE SYSTEM Filed Jan. 3, 1930 6 Sheets-Sheet 6 1712?.6, lea/56759101;

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Patented Aug. 18, 1931 UNITED STATES PATENT OFFICE TORS'IEN ADILLUNDELL, OF STOCKHOLM, SVV'EDEN, ASSIGNOR TO TELEFONAKTIE- BOLAGET II.M. ERICSSON, OF STOGK'HOLM, SW'EIDEN, A CQMIPANY OF SWEDEN TELEPHGNESYSTEM Application fi-led' January 3, 1930, Serial No. 418,380, and inSweden January 12, 1929.

the inter-oifice communications are provided with repeaters oramplifiers disposed in the through-trafiic exchange. The invention hasfor its. object to simplify the manual operation of such plants byreplacing as far as possible manual operation by automatic operation.According to the present invention the local operators positionsotherwise used in inter-ofiice plants having through-trafiic arereplaced by an automatic exchange over which the connections in questionmay be established through the intermedium or" the trunk or inter-ofiiceoperator which thus alone mediates the establishment and the supervisionof the inter-oilice communica tions.

The invention will be more closely described with reference to theaccompanying drawings. Figure 1 is a diagrammatic representation of aplant according to the invention adapted to establish amplifiedthroughcommunications. Figures 21,3, 4 and 5 are circuit diagrams for aplant according to Fig ure 1. Figures 2 and 3 illustrate thearrangements in the manually operated position whereas Figures 4 and 5show the parts of a talking connection extending through the automaticexchange. Figure 6 is a circuit diagram for the final selector. Figure 7indicates the manner of combining Figures 2, 3, 4 and 5 to form acoherent circuit diagram.

In Figure 1 the talking lines arev shown as single lines although eachline in reality comprises two or more wires. The figure shows twointer-ofiice lines 1L IL entering the telephone exchange which lines areconnected to separate operators positions EP and EP respectively overnormally closed contacts of the switching relay R11 by means of whichthe lines may be switched into direct communicationwith the automatictelephone exchange. The operators positions EP are provided with devicesto prepare the establishment of another communication over aninter-oflice line during a conversation going on at the time being. Forthis purpose each inter-office line in the operators position mayalternately be connected to the one or the other of two appertainingauxiliary lines UL and UL which at the other end are connected to theautomatic exchange. The connection of the inter-oifice line to theauxiliary lines takes place over a switch WVO and two speaking switchesE0 E0 The operators positions are provided with the necessary signallingdevices to supervise the connections and numeral switching devices toestablish the connections over the automatic exchange. The latterdevices may, by way of example, consist of a finger disk or dial or aset of buttons of the kind used in semi-automatic telephone systems.

The automatic exchange comprises distributing selectors in the form ofcall finders and also final selectors Lv LV The auxiliary lines UL ULare connected in multiple to the contact fields of the call finderswhereas the inter-ofii'ce lines are connected in multiple to thecontact. field of the line selector. Final selectors LV and LV are twoand two mutually interconnected through cord lines SL in which repeatersets FA are included and over which the interoffice communications arecompleted by associating the one final selector LV in a, set of twoselectors with the calling line and by associating the other finalselector LV with a line extending in the wanted direction. Each cordline is through an amplifier set and a line KL connected to a callfinder AS over which a connection may be established to the operatorspositon to set the final selectors and to supervise the connection.

The call finders and final selectors belonging to the automatic exchangemay,.ozt course,

be of any arbitrary kind. In the following they are assumed to beprovided with a wiper or contact arm adapted to be set in twodirections, 1. e.. to perform a turning motion to select a contact rowand a radial motion in the longitudinal direction of the wiper to selecta certain line in the contact row. They are further assumed to be of thepower-driven type and adapted to be set under the control of registersRE which in known manner may be associated with the line KL. The callfinders AS are in known manner provided with sequence switches SOS andthe final selectors are provided with sequence switches SOV SOV Also thesequence switches are power-driven. At the establishment of amplifiedcommunications; line extensions LF and line balances B, Figure 3, areapplied in a manner known per se which balances according to theinvention are adapted to be connected to the lines by means of the sameselectors Lv LV through which the connections are established. Theinter-office lines and their appertaining line balances are then assumedto be connected to the dif terent sections in the contact field of thefinal selector in such a manner that the terminals of the lines and thebalances in the corresponding sections take up the same relativepositions. The final selectors LV LV are thus provided with two sets ofcontact fields KS KS disposed on the same movable switching member,Figure 5, of which the contact sets KS bring about the connection to theline and its testing wire over the line extension LF whereas the contactset KS serves to connect up the line balance B.

The system operates as follows. Upon a call being received in theoperators position El? over the inter-office line 1L a call relay IE isactuated over a circuit 1 which relay in turn closes a circuit 2 througha call lamp IL and a relay FR which connects itself into a holdingcircuit and opens the circuit 1. The operator then shifts the speakingswitch E0 to speaking position a speaking circuit 3 being then closedthrough the operators set comprising the telephone receiver T and themicrophone M. At the same time, the interofiice line 1L is marked asengaged by a circuit 4 being closed through a relay RL which at itsnormally closed contact 5 disconnect-s the one of two rela s ltL RLassociated in parallel with the testing wire 0 in such a manner that theresistance included between the testing wires and the negative terminalof the battery is increased to a corresponding degree. After theoperator has been informed about the desired communication, she operatesinitially a switch Bli through which the testing wire of the auxiliaryline UL is connected to the ne ative terminal of the battery over acontact 6. Thereupon the operator actuates a switch SK representing thatexchange to which or over which the desired communication is to beestablished. Thereby the line UL is marked as being calling in the groupof call finders AS, the appertaining final selectors L3 of which may beconnected to the lines extending to said exchange. The latter marking iseffected by associating a fourth conductor (Z common to a group ofauxiliary lines UL with the negative terminal of the battery over acontact 7 of the switch SE Said line cl is connected to a contact barKcl appertaining to:

the contact row Ka, K6, K0, Figure 4, containing the line in question ULAt the same time a circuit 8 is closed through a relay LGR which in turncloses a circuit over its contact 9 which circuit in known manner causesthe starting of a plurality of call finders AS.

Each call finder is provided with a set of c0n-- tacts comprising tourcontact springs Fa, F6, F0 and F (Z. During the turning motion of thecall finders the contact spring FcZ successively contacts with thecontact bars Kd of the difierent contact rows. As soon as the callfinder finds the contact row which contains the'line UL in question acurrent path 10 is closed through a relay RS which is energizedandconnectsitselt' into a holding circuit over its contact 11. Saidrelay RS, closes in a manner not shown here a circuit through the clutchmagnet S0 of the sequence switch SOS, whereby the sequence switch isbrought to its third position. The circuit of the clutch magnet S0 iscontrolled in a manner known per se by a centering device CK which holdsthe circuit of the clutch magnet closed until the sequence switch hasbeen accurz tely set in the correct position.

In the third position of the sequence switch a circuit 12 is closed,whereby the relay LGR is short circuited and de-energized. Thereby allthe call finders are brought to stop. That call finder which initiallymade contact with the contact bar Kd is, however, now started in radialdirection to search the line UL marked as being calling. hen the callfinder finds this line, a circuit 13 is closed containing a relay BRwhich opens the circuits 8 and 12 whereby the selector is brought tostop. At the same time the clutch magnetot the sequence switch SOSreceives a new current impulse whereby the sequence switch is shifted tothe fourth position. In this position a circuit '14 is closed for arelay RS which is energized and connects a speaking line to the registerRE. At the same time, the sequence switch SOS is brought to the fifthposition. In this position the operator receives a buzzer signalinforming the operator that the register has been connected up. hereuponthe operator may send the impulses necessary to set the final selectors.In the shown example the operator for this purpose is using a fingerdisk or dial FS. It is assumed that each final selector is adapted to beset by means of three impulse series, the register RE being adapted toreceive six current impulse series and thereupon in due order to controlthe setting of the selectors LV and LV When the finger disk is operateda circuit 15 is closed through the one coil of the relay PR which isenergized and connects the other coil into a holding circuit 16extending over the wbranch. At the same time an impulse circuit 1'? isclosed over the b-branch which circuit'includes the impulse relay RR. ofthe register. By the impulses sent over said impulse circuit theregister is now set in known manner. In the meantime a circuit 18 hasbeen closed through a relay RV of the final selector which relay hasconnected itself into a holding circuit over its contact 19.

After completed setting of the register a circuit 20 is closed through arelay RV of the final selector. Thereby the sequence switch SOV of thefinal selector is brought to its second position in which the finalselector is started. During the turning motion of the selector, backimpulses are sent over a current path 21 which impulses in known mannercontrol a back impulse relay BB of the register RE. After completedturning motion a circuit of the relay HR of the register is opened, therelay BV being then de-energized. The sequence switch SOV is now broughtto its third position. In this position the circuit 20 is again closedthe sequence switch being then shifted to its fourth position in whichthe selector performs its radial motion. During said motion backimpulses are sent over the circuit 22 through the relay RR in theregister. After completed setting of the final selector the relay RR isagain operated, the circuit 20 being then again opened and RV thendropping its armature.

The sequence switch SOV is then brought to its ninth position. At thesame time also the sequence switch SOS is brought to its ninth position,which is the speaking position.

As will be more closely described in the following with reference toFigure 6 an interoffice line may be marked as engaged in two differentmanners. The line is namely marked as engaged in a certain manner whenthe line is engaged only by an existing talking connection and inanother manner when besides another selector is associated with a lineand standing by ready to connect itself to the line as soon as said linebecomes free. If the line is engaged and besides the final selector insaid manner is associated with the line the sequence switch SOV stops inthe ninth position as is readily understood by Figure 6. In thisposition a buzzer circuit 23 is closed through a winding of the relay RVSaid buzzer current induces a current in the operative winding of therelay which current passes through a circuit 24: including the operatorsset. By this buzzer signal the operators attention is called to the factthat the line is engaged and that another selector already is standingby ready to connect itself to the line as soon as said line he comesfree. The operator therefore clears the established communication byrestoring the switch BK to normal position, the circuit 13 through therelay RS. being then opened. When the sequence switch SOS, as aconsequence thereof,-is restored to its starting position also thecircuit 18 of the relay RV is 65 opened the sequence switch SOV togetherwith the final selectorLV being thenrestoredto normal position. a

If the line is engaged but, on the other hand, no other selector isstanding by con nected into circuit in ready position the sequenceswitch SOV stops at first in the tenth position. In said position acurrent path'25 is closed over the two line branches through theoperators set which path includes a periodical current interrupter UBwhich produces acracking noise in the operators set whereby theoperators attention is called to the fact that the. line is engaged andthat the final selector is standing by, associated with the line andready to be connected into circuit as soon as the line becomes free. Ifnow the operator while awaiting for the line becoming free desires toprepare another communication and for this purpose restores the speakingswitch EO a relay IE is connected into circuit between the two linebranches instead of the speaking apparatus. The latter relay is nowoperated by the impulses sent over the circuit 25 whereby the circuitfor a signalling lamp IL is alternately opened and closed at a contact26 of said relay. Said lamp shows thus an unsteady light so long as theline still is engaged. When the line becomes free the sequence switchSOV proceeds to its eleventh position which is the speaking position.Then the circuit 25 is opened and the lamp IL is put out.

The cord line SL has now over the selector LV been associated with theinter-office fob line IL entering the operators position E1 Aftercompleted setting of the selector LV the sequence switch SOS is broughtto its sixth position in which the final selector LV is set in similarmanner on that inter-office 1116 line, by way of example 1L with whichcommunication is wanted. After completed setting of the selector LV thesequence switch SOS is brought to its ninth position which is thespeaking position. In said posi- I10 tion the operator is connected overthe lines UL and KL to a set of relays belonging to the repeater FA saidset comprising a relay RF which is now energized over a current path 82.Thereby the line KL is associated 1-15 with a sequence switch SOV If thelatter in this moment takes up anyone of the positions 9 and 10 theoperator now receives a busy signal. It may, however, be assumed thatthe line is free and that the sequence switch SOV thus takes up theeleventh position. In said position of the sequence switch the operatordoes not notice any signal which fact thus indicates that the line isfree. If the operator wishesto ascertain if her own line is free thismight be effected by operating a key TK whereby a circuit 32 is openedand the relay RF is de-energized. The operator is then connected to thesequence switch SOV from which busy signals are obtained in position 9and 10 in above described manner in case the line should be engaged. Ifthe line is free the sequence switch takes up the position 11 in whichposition no signal is sent. It now also the own line is free twocircuits 33, 34 are closed over contacts in the sequence switches SOVand SOV and through the relay RF which is so adjusted that it isenergized at first when both of said circuits are simultaneously closed.When the relay RF is energized the line KL is disconnected from thesequence switches SOV SOV and instead connected to the repeater FA. Thena circuit 35 is closed comp-rising a relay RF which disconnects therepeater and connects the supervisory line KL to the called inter-ofiiceline. At the same time a circuit 35 is closed including a differentialcoil of the relay RL which so counteracts the previously energizedoperative winding of the same relay that the relay is de-energized, theinter-office line 1L being then again associated with the operatorsposition. The operator may now listen directly to both lines and sendcall signals. To send a call signal in the line TL, the switch R0 isactuated. By actuatinga switch R0; at circuit 37 is closed including arelay RF which connects 1L to a cal bell current source.

. As soon as the operator has ascertained that an answer is obtained inboth lines she restores the speaking switch EO to normal position therelay RF then being de-energized and restoring the coimnunica-tion withthe repeater. At. the same time, the circuit 36 is interrupted, therelay again being energized and associating the inter-ofiice line IL tothe final selector. At the same time two circuits 38, 39 are closedthrough two relays RF and RF which are energized and unite the two linesover the repeater and the appertaining line balances. The repeater maybe of any arbitrary kind and consists substantially of two amplificationdevices F F and two difierential transformers DT DT A clearing signalfrom the one or the other line operates a relay 11F or R1 respectivelywhich in turn closes a circuit 40 through a coil of the relay RF whichthen connects its holding coil into a circuit ll. which also includesthe relay RF The latter relay is, however, not energized in this case.On the other hand, the relay 1R of the operators position is actuatedwhich relay over its contact 26 connects the signalling lamp 1L intocircuit. The operator may now by shifting her speaking switch E0, in theabove described manner put herself into communication with both lines.Finally the automatic connection is interrupted by restoration of theswitch BK to normal position.

It has been assumed above that the final selectors are set on a certaindefinite line.

In reality the final selector has to choose between a plurality of linesextending to the same exchange and the selector will for this reasonupon being set on the first of the lines extending to the exchange inquestion, automatically search a line free for the time being. Thesystem is, according to the invention, so arranged that in case alloutgoing lines should be engaged the selector is set in a stop positionimmediately after the contacts of the last line whereupon the selectorreturns over the same contacts while testing the lines anew. In saidposition the testing circuit of the selector has, however, been shiftedin such a manner that the selector during its return motion may be seton a line engaged for the time being without establishing communicationwith said line. At the same time said line is blocked for otherselectors in such a manner that only one selector may remain standing byin the line, ready to be associated as soon as the line becomes free.The testing arrangement is then of such a nature that the selectorduring its return motion is passing such lines on which another selectoralready is set in ready position. During the return motion the selectormay, of course, also stop on a line which meanwhile has been madeentirely free.

Said switching operation is illustrated in Figure 5 showing only thosecircuits which have any relation to the testing. After comnleted settingof the selector on the first of the lines extending to the wantedexchange which line is connected to a contact position, designated 1 onthe drawings, the sequence switch SOV is shifted to its sixth positionin which position the selector is again started to search a free line,in case the first line should be engaged. The starting is effected by acircuit 42 which actuates a magnet GRV which, in turn, closes a circuit4L3 of the clutch magnet controlling the motion of the selector into thecontact field in radial direction. As is readily understood from Figure2, a line is marked as engaged as soon as the relay RL is energized.When testing the line there takes place a flow of current 441-, Figure5, through the testing relay RG but this flow of current is insufficientto actuate RF First when the selector reaches atree line the testingrelay RF is sufliciently energized as the test wire of the line in thiscase is connected to the negative terminal of the battery over bothrelays RL RL If the line should be engaged by a communication notpassing through the operators position, byway of example an amplifiedcommunication, the testing relay RG may, anyhow, not attract itsarmature, be cause said relay is then connected in parallel with asimilar relay in another selector and hence does not obtain sufficientcurrent. As soon as the selector finds a tree line the relay RG however,operated, the clutch magnet of the sequence switch then being energizedover a current path 45'so as to bring the sequence switch to itseleventh position being the speaking position.

If all the lines should be engaged the selector continues'its motionuntil it reaches its stop position which in Figure 5 is designated S Insaid position a circuit 46 is closed which is branched in parallelthrough the relaysRGr and RG which now both attract their armatures.WVhen the relay RG attracts its armature a circuit 47 for the relayRGQis closed which relay is now energized and locks itself over acircuit a8. At the same time the relay RG is disconnected. Further acircuit 49 is closed through the clutch magnet of the sequence switchwhereby the sequence switch is brought to its seventh position. In saidposition the magnet GRV is energized over the contact 50 in the sequenceswitch a circuit 51 being then closed through the magnet MVV whichcauses a reversing of the motion of theselector, the selector now movingbackward in the same contact row. When the selector leaves the stopposition the relay RG is deenergized whereby the test wire is connectedto a testing relay RG The latter relay is so dimensioned that it mayattract its armature even if the line, for the time being, is engaged bya communication. On the other hand, it may not attract its armature ifthe line is engaged by a communication and at the same time anotherselector is associated with the line in ready position. In the lattercase the c-wire of the line is namely connected both to the negativeterminal of the battery over a relay ItL if the line is engaged by acommunication passing through the own operators position, and to thepositive terminal of the battery over a relay RG in a selector in readyposition. If the line should not be engaged in the own operatorsposition the test wire of the line is connected to the positive pole ofthe battery over two parallel-connected relays RG In both cases.

the current received by the testing relay RG is insuflicient to operatethe relay and the selector continues its motion until it finds either aline which in the meantime has become entirely free or a line which isengaged and on which no selector is set in ready position. Should allthe lines during the return motion be marked as entirely engaged, i. e.if the selector is set in ready position on each one of the lines theselector continues its return motion until it reaches the stop positionS immediately in front of the first position. In said position therelays RG and RG obtain sufficient current to be actuated the sequenceswitch being then operated over a circuit 52 and, as a consequence,brought to its ninth position in which position the selector stops and abusy signal is sent to the operator. g

If the selector during its return motion should find a line which isengaged but on which no other selector is set in ready position therelay RG is sufiiciently energized over the test wire to be able toattract its armature the sequence switch then receiving current over acircuit 53 and thereby being brought to its tenthposition in whichposition the selector remains standing by in ready position until theline becomes free. In the tenth position of the sequence switch, thecircuit 48 is interrupted and the relay HG,L consequently de-energized.The relay RG has thus now been disconnected and instead the testingrelay RG has been asso ciated with the test wire. When the line becomesfree, the relay RG attracts its armature which results in that thesequence switch is brought to its eleventh position which is thespeaking position.

I claim: 1. A switching arrangement to establish inter-ofiice transit orthroughecommunications betweenthe lines entering a telephone exchangefrom other telephone exchanges and more especially inter-ofiicecommunications having repeaters or amplifiers, characterized in thatsaid lines are associated in multiple with final selectors which are twoand two mutually interconnected through cord lines in which amplifiersmay be included and over, which the inter-office commun cations line andthe other line selector to a line eX- tending in the wanted direction,said cord lines being adapted to be connected over distributingselectors to auxiliaryor supervisory linesv extending from theinter-ofiice operators, positions over which lines the selectors may beoperated and the intenoffice communications supervised.

, 2. A switching arrangement as claimed in claim 1 in which the finalselectors are set under the control of registers, characterized in thatthe registers are adapted to receive impulses, sent from theinter-ofiice operator and corresponding to the number of both the linesto be connected with one another, and to control, in order of sequence,the setting of the two final selectors, belonging to the same selectorpair. I r

3. A switching arrangement as claimed in claim 1, characterized in thateach selector pair is provided with a sequence switching device wherebythe switching is controlled in such a manner that the junction line isinitially connected in turn to the two selectors to set said selectorsand thereupon connected to the amplifier to control the communication.

t. A switching arrangement as claimed in claim 1, characterized inthatthe calling line is adapted to be associated alternately to theinter-ofiice operators position and to the final selector multiple bymeans of a switching arrangement adapted to be controlled from theoperators position. v

5. A switching arrangement as claimed in claim 1, characterized in thatline balances B appertaining to the inter-oifice line are adapted to beassociated with the lines by means of selectors LV adapted to be setfrom the interoffice operators position.

6. A switching arrangement as claimed in claim 1, characterized by anarrangement to switch the testing circuit of those line selectors whichestablish communication with a wanted line said switching arrangementwhen all lines extending in the wanted direction are engaged, bringingabout such an alteration in the testing circuit that the selector may beset in ready position on an engaged line without establishingcommunication therewith.

I 7. A switching arrangment as claimed in claim 1 characterized in thatthe calling line is adapted to be associated alternately to theinter-ofice operators position and to the final selector multiple bymeans of a switch arrangement adapted to be controlled by the operatorsposition, said switching arrangement being adapted to be operated fromthe operators position of the supervisory line.

8. A switching arrangement as claimed in claim 1, characterized in thatthe line balances appertaining to the inner-oifice line are adapted tobe associated with the lines by means of selectors adapted to be setfrom the innerbifice operators position, the line balances being adaptedto be conducted by means of the same final selectors by means of whichcommunications are established.

9. A switching arrangement as claimed in claim 1, characterized in thatthe line balances appertaining to the inner-oflice line, are adapted tobe associated with the lines by means of selectors adapted to be setfrom the inner-oifice operators position, characterized in that thelines and their balances are connected to separate sections in thecontact field of the final selector in which sections the terminals ofthe lines and the balances take up the same relative positions.

16. A switching arrangement as claimed in claim 1, characterized by anarrangement to switch the testing circuit of those line selectors whichestablish communication with a wanted line, said switching arrangement,when all lines extending in the wanted direction are engaged, bringingabout such an alteration in the testing circuit that the selector may beset in ready position on an engaged line without establishingcommunication therein, the disposition of the selector being such thatthe selector when searching a wanted line, passes such lines in which another selector already is set in ready position.

11. A switching arrangement as claimed in claim 1, characterized by anarrangement to switch the testing circuit of those line selectors whichestablish communication with a wanted line, said switching arrangement,

when all lines extending in the wanted direction are engaged, bringingabout such an alteration in the testing circuit that the selector maybeset inready position on an engaged line without establishingcommunication therewith, wherein those arrangements

